Numerical ages

 

Age models are based on age-depth plots for every hole, that were constructed with the help of an interactive graphics application called Age-Depth Plot (ADP). This program was originally written by David Lazarus in True Basic programming language and designed for the 68 generation of Macintosh. Meanwhile, ADP was first recompiled for usage on PowerMacintosh (ADP PPC). In order to provide platform independent versions, ADP was re-written in 4D, and can be downloaded from this server as standalone applications for MacOs and PC/NT operating systems. All versions can be downloaded from the NEPTUNE-online II server.

 

With ADP age-depth diagrams can be constructed interactively by visual graphical correlation. Input data are the vertical distribution of first appearance (FAD) or last appearance datums (LAD) of stratigraphic events along a core. The program allows to plot the datums in age-depth scatter diagram and then to manually interprete a line segments of most reasonable fit. The control points of the line segments can be exported as a "line of correlation"- (LOC) file in ascii text format.

 

All datums of Cenozoic events follow the integrated chronology of Berggren et al. (1995). If necessary the age assignments for the included microfossil datums (i.e. planktonic foraminifera, coccoliths, radiolaria, diatoms, bolboforma) were magnetically converted to the Cande and Kent (1995) magnetic polarity time scale.

 

An extended age model collection for DSDP and ODP holes was prepared, using oxygen isotope events, marine strontium isotope stratigraphy and bolboforma stratigraphy. For the Pleistocene to Holocene Period oxygen isotope stage boundaries and events were included as well. For this the nomenclatures of isotope events of Prell et al. (1986) and Ruddiman et al. (1989) were applied. Oxygen isotope datums were magnetically converted to the Cande and Kent (1995) magnetic polarity time scale. The datums of events 1.1 through 16.23 were taken from Imbrie et al. (1984), those from event 17.1 on from Shackleton et al. (1990), and the ogygen isotope chronology was extended back to the Early Pleistocene using the O-isotope stratigraphy of Williams et al. (1988). Sr 87/86 ratios were integrated where possible, using the Marine Sr Isotope Curve of Howarth and McArthur (1997). Ages of marine Sr 87/86 ratios between 0 and 7 Ma have also been converted to the Cande and Kent (1995) magnetic polarity time-scale. The bolboforma stratigraphy follows that of Spiegler and von Daniels (1991), that was extended and calibrated to the Cande and Kent (1995) time-scale.

 

For the construction of age the models presented here the FAD and LAD intervals of each stratigraphic event, as well as the necessary information of the depths of the core-tops, core-lengths and recovery were taken from the respective Initial and Scientific Reports of the DSDP and ODP and the coring summaries therein. The names and ages of stratigraphic events per microfossil group per geographic area are listed in text formats in Excel spreadsheets (=templets). These templets formed the basis to compile the age-depth information of the FADs and LADs of stratigraphic events. See links leading to Templets (Mac or PC archives).

 

The data containing the actual stratigraphic distribution of microfossils or events per site (only FADs and LADs) are stored in single ascii text files. See links directing to Bstrat files (Mac or PC archives).